REGRESSION(r163850): INPUT doesn't respond to keyboard input after DATALIST availability change.

When an associated DATALIST element gets a valid OPTION element, the inner
editor element in the INPUT is detached from the DOM tree, and attached
again. It makes selection state incomplete. We need to restore selection
information.

Note: HTMLInputElement::updateFocusAppearance needs to be public
in order to be called from TextFieldInputType.


BUG=349846
TEST=automated

Review URL: https://codereview.chromium.org/190193003

git-svn-id: svn://svn.chromium.org/blink/trunk@168722 bbb929c8-8fbe-4397-9dbb-9b2b20218538